The Lincoln Club has been mailing out ads critical of Fletcher, saying he’s a flip-flopper and doesn’t show up for work.

A Lincoln Club spokeswoman said the group has no knowledge why at least four prominent members gave to Alvarez.

“The Lincoln Club does not have direct knowledge as to why contributors support any of the candidates,” spokeswoman Erica Holloway said in a statement. “Contributions to our organization’s general fund supports all our varied efforts.”

Lincoln Club donor David Malcolm said he gave to Faulconer because he agrees with him on more issues. But he said he has a soft spot for Alvarez and so gave to him, too.

“I’d love to see someone out of the South Bay win,” said Malcolm, a former port commissioner who also served on the Chula Vista City Council.

“He’s a guy who’s pro-business and is reasonable in his approach,” Malcolm said of Alvarez. “I don’t agree with him all the time, but he’s thoughtful and bright.”

Republican Christopher Garrett, a partner with Latham & Watkins, is another donor to both Alvarez and Faulconer.

“I prefer Kevin Faulconer’s stand on many of the current issues in the race, but I also believe David Alvarez is an honest and hardworking person who listens to both sides and brings an important perspective to many issues,” he said.

Alvarez said he did not believe his campaign was the benefactor of those who have a strategy to help him win a top-two spot in the Nov. 19 general election, to then lose in a runoff.

“Investing in neighborhoods is not a partisan issue. There’s no Democratic or Republican way to fill a pothole,” Alvarez said. “The people who give to my campaign are people who live in and care about San Diego. They have lived with the neglect of our roads, playgrounds, and parks and they like my blueprint for San Diego’s future.”

A spokesman for the Faulconer campaign declined to comment. A spokeswoman for Fletcher’s campaign did not return a call seeking comment.